[BPF] generate btf_decl_tag records for params of extern functions

[eddyz87]

Summary

After frontend changes in the following commit:
"BPF: preserve btf_decl_tag for parameters of extern functions"
same mechanics could be used to get the list of function parameters
and associated btf_decl_tag entries for both extern and non-extern
functions.

This commit extracts this mechanics as a separate auxiliary function
BTFDebug::processDISubprogram(). The function is called for both
extern and non-extern functions in order to generated corresponding
BTF_DECL_TAG records.

Depends on D140970

[eddyz87]

This comment was removed by eddyz87.

[eddyz87]

Replace test case DIFile name and checksum with fake values to avoid
potential missmatches in strings produced by BTFDebug::constructLineInfo().

[eddyz87]

Fix for clang-format issue reported by CI.

llvm/lib/Target/BPF/BTFDebug.h

class BTFDebug : public DebugHandlerBase {
 
   /// Generate types for function prototypes.
   void processFuncPrototypes(const Function *);
 
   /// Generate types for decl annotations.
   void processDeclAnnotations(DINodeArray Annotations, uint32_t BaseTypeId,
                               int ComponentId);
 
+  /// Generate types for DISubprogram and it's arguments.
+  uint32_t processDISubprogram(const DISubprogram *SP, uint32_t ProtoTypeId,
+                               uint8_t Scope);
+
   /// Generate BTF type_tag's. If BaseTypeId is nonnegative, the last
   /// BTF type_tag in the chain points to BaseTypeId. Otherwise, it points to
   /// the base type of DTy. Return the type id of the first BTF type_tag
   /// in the chain. If no type_tag's are generated, a negative value
   /// is returned.
   int genBTFTypeTags(const DIDerivedType *DTy, int BaseTypeId);
 
   /// Generate one field relocation record.

llvm/lib/Target/BPF/BTFDebug.cpp

for (const Metadata *Annotation : Annotations->operands()) {
 
     const MDString *Value = cast<MDString>(MD->getOperand(1));
     auto TypeEntry = std::make_unique<BTFTypeDeclTag>(BaseTypeId, ComponentIdx,
                                                       Value->getString());
     addType(std::move(TypeEntry));
   }
 }
 
+uint32_t BTFDebug::processDISubprogram(const DISubprogram *SP,
+                                       uint32_t ProtoTypeId, uint8_t Scope) {
+  auto FuncTypeEntry =
+      std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
+  uint32_t FuncId = addType(std::move(FuncTypeEntry));
+
+  // Process argument annotations.
+  for (const DINode *DN : SP->getRetainedNodes()) {
+    if (const auto *DV = dyn_cast<DILocalVariable>(DN)) {
+      uint32_t Arg = DV->getArg();
+      if (Arg)
+        processDeclAnnotations(DV->getAnnotations(), FuncId, Arg - 1);
+    }
+  }
+  processDeclAnnotations(SP->getAnnotations(), FuncId, -1);
+
+  return FuncId;
+}
+
 /// Generate btf_type_tag chains.
 int BTFDebug::genBTFTypeTags(const DIDerivedType *DTy, int BaseTypeId) {
   SmallVector<const MDString *, 4> MDStrs;
   DINodeArray Annots = DTy->getAnnotations();
   if (Annots) {
     // For type with "int __tag1 __tag2 *p", the MDStrs will have
     // content: [__tag1, __tag2].
     for (const Metadata *Annotations : Annots->operands()) {
void BTFDebug::beginFunctionImpl(const MachineFunction *MF) {
   }
 
   // Construct subprogram func proto type.
   uint32_t ProtoTypeId;
   visitSubroutineType(SP->getType(), true, FuncArgNames, ProtoTypeId);
 
   // Construct subprogram func type
   uint8_t Scope = SP->isLocalToUnit() ? BTF::FUNC_STATIC : BTF::FUNC_GLOBAL;
-  auto FuncTypeEntry =
-      std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
-  uint32_t FuncTypeId = addType(std::move(FuncTypeEntry));
-
-  // Process argument annotations.
-  for (const DINode *DN : SP->getRetainedNodes()) {
-    if (const auto *DV = dyn_cast<DILocalVariable>(DN)) {
-      uint32_t Arg = DV->getArg();
-      if (Arg)
-        processDeclAnnotations(DV->getAnnotations(), FuncTypeId, Arg - 1);
-    }
-  }
-
-  processDeclAnnotations(SP->getAnnotations(), FuncTypeId, -1);
+  uint32_t FuncTypeId = processDISubprogram(SP, ProtoTypeId, Scope);
 
   for (const auto &TypeEntry : TypeEntries)
     TypeEntry->completeType(*this);
 
   // Construct funcinfo and the first lineinfo for the function.
   MCSymbol *FuncLabel = Asm->getFunctionBegin();
   BTFFuncInfo FuncInfo;
   FuncInfo.Label = FuncLabel;
void BTFDebug::processFuncPrototypes(const Function *F) {
 
   // Do not emit again if already emitted.
   if (!ProtoFunctions.insert(F).second)
     return;
 
   uint32_t ProtoTypeId;
   const std::unordered_map<uint32_t, StringRef> FuncArgNames;
   visitSubroutineType(SP->getType(), false, FuncArgNames, ProtoTypeId);
-
-  uint8_t Scope = BTF::FUNC_EXTERN;
-  auto FuncTypeEntry =
-      std::make_unique<BTFTypeFunc>(SP->getName(), ProtoTypeId, Scope);
-  uint32_t FuncId = addType(std::move(FuncTypeEntry));
-
-  processDeclAnnotations(SP->getAnnotations(), FuncId, -1);
+  uint32_t FuncId = processDISubprogram(SP, ProtoTypeId, BTF::FUNC_EXTERN);
 
   if (F->hasSection()) {
     StringRef SecName = F->getSection();
 
     if (DataSecEntries.find(std::string(SecName)) == DataSecEntries.end()) {
       DataSecEntries[std::string(SecName)] =
           std::make_unique<BTFKindDataSec>(Asm, std::string(SecName));
     }

llvm/test/CodeGen/BPF/BTF/tag-extern-func.ll

+; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+
+; Source code:
+;   #define __tag(x) __attribute__((btf_decl_tag(x)))
+;
+;   extern void foo(int x __tag("x_tag"), int y __tag("y_tag")) __tag("foo_tag");
+;
+;   void root(void) {
+;     foo(0, 0);
+;   }
+; Compilation flag:
+;   clang -target bpf -O2 -g -S -emit-llvm test.c
+
+
+; Function Attrs: nounwind
+define dso_local void @root() local_unnamed_addr #0 !dbg !7 {
+entry:
+  tail call void @foo(i32 noundef 0, i32 noundef 0) #2, !dbg !12
+  ret void, !dbg !13
+}
+
+declare !dbg !14 dso_local void @foo(i32 noundef, i32 noundef) local_unnamed_addr #1
+
+attributes #0 = { nounwind "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #1 = { "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 16.0.0 (https://github.com/llvm/llvm-project.git 603e8490729e477680f0bc8284e136ceeb66e7f4)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "fake-file-name.c", directory: "fake-directory", checksumkind: CSK_MD5, checksum: "00000000000000000000000000000000")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 7, !"frame-pointer", i32 2}
+!6 = !{!"clang version 16.0.0 (https://github.com/llvm/llvm-project.git 603e8490729e477680f0bc8284e136ceeb66e7f4)"}
+!7 = distinct !DISubprogram(name: "root", scope: !8, file: !8, line: 5, type: !9, scopeLine: 5, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!8 = !DIFile(filename: "fake-file-name.c", directory: "fake-directory", checksumkind: CSK_MD5, checksum: "00000000000000000000000000000000")
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !{}
+!12 = !DILocation(line: 6, column: 3, scope: !7)
+!13 = !DILocation(line: 7, column: 1, scope: !7)
+!14 = !DISubprogram(name: "foo", scope: !8, file: !8, line: 3, type: !15, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !18, annotations: !25)
+!15 = !DISubroutineType(types: !16)
+!16 = !{null, !17, !17}
+!17 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!18 = !{!19, !22}
+!19 = !DILocalVariable(name: "x", arg: 1, scope: !14, file: !8, line: 3, type: !17, annotations: !20)
+!20 = !{!21}
+!21 = !{!"btf_decl_tag", !"x_tag"}
+!22 = !DILocalVariable(name: "y", arg: 2, scope: !14, file: !8, line: 3, type: !17, annotations: !23)
+!23 = !{!24}
+!24 = !{!"btf_decl_tag", !"y_tag"}
+!25 = !{!26}
+!26 = !{!"btf_decl_tag", !"foo_tag"}
+
+; CHECK:  .long 0                               # BTF_KIND_FUNC_PROTO(id = 1)
+; CHECK-NEXT:   .long 218103808                       # 0xd000000
+; CHECK-NEXT:   .long 0
+; CHECK-NEXT:   .long 1                               # BTF_KIND_FUNC(id = 2)
+; CHECK-NEXT:   .long 201326593                       # 0xc000001
+; CHECK-NEXT:   .long 1
+; CHECK-NEXT:   .long 0                               # BTF_KIND_FUNC_PROTO(id = 3)
+; CHECK-NEXT:   .long 218103810                       # 0xd000002
+; CHECK-NEXT:   .long 0
+; CHECK-NEXT:   .long 0
+; CHECK-NEXT:   .long 4
+; CHECK-NEXT:   .long 0
+; CHECK-NEXT:   .long 4
+; CHECK-NEXT:   .long 44                              # BTF_KIND_INT(id = 4)
+; CHECK-NEXT:   .long 16777216                        # 0x1000000
+; CHECK-NEXT:   .long 4
+; CHECK-NEXT:   .long 16777248                        # 0x1000020
+; CHECK-NEXT:   .long 48                              # BTF_KIND_FUNC(id = 5)
+; CHECK-NEXT:   .long 201326594                       # 0xc000002
+; CHECK-NEXT:   .long 3
+; CHECK-NEXT:   .long 52                              # BTF_KIND_DECL_TAG(id = 6)
+; CHECK-NEXT:   .long 285212672                       # 0x11000000
+; CHECK-NEXT:   .long 5
+; CHECK-NEXT:   .long 0
+; CHECK-NEXT:   .long 58                              # BTF_KIND_DECL_TAG(id = 7)
+; CHECK-NEXT:   .long 285212672                       # 0x11000000
+; CHECK-NEXT:   .long 5
+; CHECK-NEXT:   .long 1
+; CHECK-NEXT:   .long 64                              # BTF_KIND_DECL_TAG(id = 8)
+; CHECK-NEXT:   .long 285212672                       # 0x11000000
+; CHECK-NEXT:   .long 5
+; CHECK-NEXT:   .long 4294967295
+
+; CHECK:  .ascii  "int"                           # string offset=44
+; CHECK:  .ascii  "foo"                           # string offset=48
+; CHECK:  .ascii  "x_tag"                         # string offset=52
+; CHECK:  .ascii  "y_tag"                         # string offset=58
+; CHECK:  .ascii  "foo_tag"                       # string offset=64